Solenoid



W. F. KELLEY SOLENOID March 21, 1939.

Filed Dec. 3, 1937 FIG .3

FIGA

FIG.5

FIGJ

II Il INVENTOR WALTER F. KELLEY ATTORNEY Patented Mar. 2l, 1939 unirseSTATES SOLENOID Walter F. Kelley, Whitestone, N. Y., assignor ltoRemington Rand Inc., Buialo, N. Y., a corporation of DelawareApplication December 3, 1937, Serial No. 177,924

3 Claims.

This invention relates to solenoids and more particularly toimprovements in solenoids which include `a movable core or plungeras'part of their mechanism.

Solenoids with movable cores designed to actuate other mechanisms by achange ofcurrent in their windings, possess many advantageouscharacteristics, such as high operating eiiciency, small space required,and quick action. Consequently, they have been employed inl many 'mafchines in a variety of designs,

The solenoid described hereinafter includes a casing which encloses allthe moving parts, a fully protected winding. and a plunger which hasmany unique features.

The principal object of this invention is to provide a solenoid with aplunger which will not Other objects and structural details of the inlvention will be apparent from the following description when read inconnection with the accompanying drawing, wherein:

Fig.` 1 is a central section view of the entire assembly;

Fig. 2 is a section taken along line 2-2 of Fig. 1;

Fig.3 is a plan view of the insulating end disc which holds theelectrical wiring in place;

Fig. 4 is a plan view of the slotted washer of insulating material whichholds tls terminal Wires;

Fig. 5 is a plan view of a slotted phosphor bronze washer for supportingthe winding;

Fig. 6 is a bottom view of the plunger showing the eddy current slots.

Although the solenoid is not necessarily in a vertical position when inuse, it is always inclined enough to allow the plunger to be drawn backto its normal position by gravity. In this description the solenoid willbe considered as standing in. a vertical position (Fig. l) and the upperportion will be called the top, while the lower portion will be calledthe bottom.

The fundamental principle underlying the op-l eration of power solenoidsis, that the production of motion is accomplished when and only whensuch motion reduces the reluctance of the entire magnetic circuit. Thetotal reluctance of any magnetic ciruit is equal to the combinedreluctances of the separate parts, and if these parts are connected inseries, then the total reluctance is equivalent to the algebraic sum ofthe parts. Since the magnetic ilux must enter a free plunger or armatureat one point and leave it at another, there are always two air gaps inthe magnetic circuit when the plunger is inv its position correspondingto a value of current equal to zero. When the solenoid current is causedto flow, the plunger or armature moves in a direction tending to shortenone or both air gaps and hence reduce the reluctance in the magneticcircuit. The presend invention employs a design in which only one airgap is reduced, the other remaining constant. Hereinafter, the two airgaps will be designated as variable and constant, it being understoodthat the variable air gap produces the power necessary for motion andthe constant air gap produces no power at all.

The outside casing of the solenoid consists of a soft iron tube I0,which isturned in at the bottom to form an annular shoulder II therebyforming a hole I2 in the bottom of the casing, large enough for thepassage of an iron plunger 5) and an insulating disc I6 which forms partof A the coil assembly. r

Inside the metal tube I5 is placed another tube I8 of phenol resin asshown (Fig. 1). This tube provides a low friction surface for the bottcmshoulder of the plunger to slide on and furl ther helps to denitelydetermine the equivalent airv gap in this portion of the magneticcircuit.

The solenoid winding Il is wound upon a tube 20 made of phenol resin andis supported at ITI SEI)

. I3 together-with its bottom flange member I4, as

each end by insulator discs I6 and 2|. The winfiing is protected on theoutside by the iron cas- Aing I0. The upper insulator disc 2l containstwo' notches 22 and 23 (Fig, 3), said notches being provided to permitthe passage of the two ends of the solenoid winding, 24 and 25 (Fig. 2)

through the disc 2| to their respective connections. A guide ring 26.composed of insulation material (Fig. 4) containing a slot 21 is placedon the disc 2I so that the notch 23 of disc 2I is in line with the slot2l. This arrangement permits a wire to pass through the notch and slotas shown in Fig. 2.

The ends 24 and 25 (Fig. 2) of the solenoid winding Il are soldered toWires 30 and 3l, which wires in turn are Wound around the ring 2Bone-half of a turn and then passed through holes in a cap member 34. Theinsulation of the wires is slightly thicker than the ring 23 so thatwhen the wires are placed in position, they protrude over the top of thering. A shoulder 35 is formed in the top of casing lll on whichshoulder, cap 34 is positioned. The upper edge of cap 34 is chamfered topermit the edge of casing Ill to be turned over the ehamfer and therebypermanently fasten the cap together with the sole noid winding Il, inplace. When the easing I0 is crimped over the edge of the cap 34, saidcap will be forced down until it engages shoulder 35. Since theinsulation of the wires 30 and 3l is slightly thicker than the ring 26,the Wires are consequently compressed by the cap 34 and tightly held inplace. This prevents any movement of the wires at their soldered joints,thereby protecting them from breaking.

Secured to the cap 34 is a nipple 36 which is provided with a concentrichole 31, used as a guide for a. non-magnetic rod 38 that may be fastenedto the plunger of the solenoid or engaged by it. The nipple 36 isfurther provided with a bottom extension piece 40 which fits lnside theinsulator tube .20 and is partly supported therein. The nipple 36 issecured to the cap 34 by bolts or rivets or the two may be integrallycut from the same piece. A thread 4I is cut on the nipple 36 asindicated to aid in securing any mechanism which may be used to transmitthe actuated plunger impulse. i

The plunger I3 oi' the solenoid rides inside of the tube 2U, said tubeacting as a bearing for the plunger. In order to eliminate any bindingaction which might occur due to misalignment, a shoulder 42 is providedat the upper end of the plunger I3, the diameter of said shoulder beingslightly smaller than the diameter of the insu lator tube 20. Thediameter of the remaining cylindrical portion is slightly less than thediameter of the shoulder so that the only point of contact between lthecylinder 20 and plunger I3 is the shoulder 42.

At the bottom of the plunger I3, the flange member I4 is attached by anyof the well known methods or the entire plunger and bottom flange may beturned from a solid piece of metal. The diameter of the ange is slightlyless than the inside diameter of the phenol resin tube I8 in order toprovide freedom of motion throughout the length of said tube withoutpermitting any serious change in air gap length.

The space between the flange I4 and the inside iron tube I5 is termedair gap even though the space is filled almost entirely with phenolresin. Such parlance is common among those skilled in the art and isjustified because the magnetic permeability of the phenol resin is thesame as that of air. The air-gap in this face may vary depending uponother design factors and magnetic characteristics of the iron used. Inany event the reluctance of this constant air gap may be made quitesmall in comparison to the variable air gap, because the area is solarge.

Winding I1.

'I'he area extends around the periphery of the flange and is furtherenlarged by adding an extension 43 to the upper edge of the flange asshown.

A soft rubber washer 44 is placed on the cylindrlcal portion oi' theplunger I3, next to the flange I4 to act as a resilient shock absorberat the end of theplunger stroke. Another soft rubber washer 45 is placedinside the casing next to the shoulder Il and forms a cushion for theplunger to fall upon when it returns under the force of gravity, afterthe magnet has been deenergized. This rubber washer 45 also forms aconvenient means for holding the plunger within the casing when in useor for removing it for inspection. Removal is accomplished by distortingthe washer so that it may be taken out through the hole I2 after whichthe plunger slides out Without further obstruction.

When the coil is energized, a strong magnetic ileld is set up in thesoft iron components and in the two air gaps. The path of these magneticlines is as follows: From the plunger I3 where the greatest fieldstrength is maintained, through the variable air gap 46, to the nippleextension 40, spreading out through the cap 34, down through the easingIl), into the tubing I5, across the constant air gap to the flange I4and back to the plunger I3. Since a movement of the plunger I3 upwardwill shorten the variable air gap 46 and not change the constant airgap, the plunger will move up unless restrained by a force greater thanthat set up by the magnetic iield. Assuming that the plunger is not sorestrained, it moves swiftly upward gaining in tractive force as thevariable air gap is shortened until the rubber washer 44 strikes thephosphor bronze ring I9 and stops the plunger motion. The top surface ofthe plunger never reaches the bottom surface of nipple extension 40because the parts are so proportioned that the washer 44 stops theupward movement just short of contact.

Because freedom for motion must be provided between the flange and thetubular phenol guide, it follows that these parts may be eccentric bythe necessary clearance and that the air gap at opposite ends of adiameter may vary by double the normal clearance distance. This tends tounbalanee the magnetic eld and the consequent radial or side-actingforces on the fiange. The construction is also vfor the purpose ofkeeping the clearance at a minimum in order to maintain a minimumunbalance of the radial forces and friction.

The fact that the phenol tubing I8 constrains the flange I4 to a smalllateral motion also keeps the main plunger I3 in line with the phenoltubing 20 which forms the inside of the electrical The dimensions aresuch that the only contact the plunger I3 can make with the phenoltubing 2 0, is at the topmost portion 42, which by reason of its largerdiameter, holds the remaining portion of the plunger clear.

The net result of this form of structure is a continuously alignedplunger with a constant low reluctance air gap at the flanged portion,and negligible friction due to lateral attraction.

While I have described what I consider to be a highly desirableembodiment of my invention, it is obvious that many changes in formcould be made without departing from the spirit of my invention, and I,therefore, do not limit myself to the exact form herein shown anddescribed, nor to anything less than the whole of 75 my inventionv ashereinbefore set forth, and as hereinafter claimed.

What I claim as new, and desire to secure by Letters Patent, is:

1. In a solenoid having a tubular iron casing, a coil within saidcasing, an iron plunger axially movable partly within said coil andpartly within said casing, iron flanges at each end of said plunger, theiiange within said coil being only slightly larger than the plunger, theiiange within said casing being at least twice as large as the plunger,the periphery of each ange formed with a cylindrical surface concentricwith the plunger, tubes of non-magnetic material mounted Within the saidcoil and within the said iron casing, whereby the periphery of thelarger flange is movable within said tubing along the axis thereof butis laterally constrained to less than ten per cent of the distancebetween said ange and said tubular iron casing.

2. In a solenoid having a tubular iron casing, a coil within saidcasing, a movable iron plunger within said coil of cylindrical formhaving anged end portions, each having a diameter larger than thediameter of the middle portion thereof, two phenol resin tubularmembers, one positioned inside of said coil to slidably engage thesmaller of said plunger flanges, the other positioned outside of saidcoil but inside of said casing to slidably engage the larger of saidplunger anges, the larger ange being at least twice the diam eter of thesmaller ilange.

3. In a solenoid having an iron casing, a coil and a movable ironcylindrical plunger, an iron ilange formed on each end of said plunger,said flanges provided with coaxial cylindrical peripheries each having adiameter larger than the diameter of the middle portion of said plunger,one of said flanges being slidably mounted within said coil, the secondiiange being slidably mounted within a non-magnetic tube adjoining thesaid casing, the second of said flanges being at least twice thediameter of the smaller iiange and both flange portions forming serieselements in the magnetic circuit of said solenoid.

WALTER. F. KELLEY.

